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Dealing with runs....2/25/18
I basically only finish cabinet doors, panels, trim, etc.
Since switching to the AAA sprayer, I've had issues with runs on the edges of the doors that have a 1/4" roundover edge.
Basically, what's happening is that 1/4" roundover is getting hit on a pass when I do my edges, and then is getting hit when I box coat the face of the door.
Since the 1/4" roundover is a radius, the excess material from the 2 passes (1 edge - 1 face) starts to run, creating bumps and "runs" on the door edge.
Any tips on what to do here? I'm spraying the face at about a 3-4 wet mil thickness. The edges I'm barely hitting because I'm so nervous about this situation.
Thanks for the tips. I'll try them all. The sales rep said something like 85%transfer efficiency.
No idea what product you are spraying. Possibly work two doors at once. Spray the edges on one, set it aside. Then spray the edges on a second one and set it aside. Then go back on do the face on 1 and then the face on 2. Gives it a chance to flash off a little on the edges.
That's an interesting idea.
I know the problem is my technique while using the AAA system.
Happened to me with magnamax, magnaklear, and now with Krystal cv.
Well, obviously the air pressure, the material viscosity, and orifice size are what determines your spray pattern recommendations. IT is really tough to tell you what the issue is without knowing all of these things.
I personally set my gun so I have a 66% overlap in my pattern.
When it comes to corners, rounds, or returns, when I get close to to corner I will pull the gun back to allow it to dry spray a little, then I will pass that area twice, from both sides if necessary.
Do not ever try to get full coverage in one coat.
Always remember to spray a tac coat to promote adhesion of sequential coats.
A tac coat is to spray lightly to allow a light mist to collect of the substrate. Doing so allows the dry spray do tac up somewhat then spray right over the tac coat withing a couple minutes.
Remember you can not one coat anything no matter what those stupid TV commercials tell us.
Do not sprat the corner directly, let the dry spray collect and the layers to do their jobs.
Do not force it young Padiwan. Use the force.
Which pump/gun..... what is the full tip# your using...post the products your using.... tell us what your fluid pressure and air atomizing pressure is while spraying... Then we can give you some solid advice....
I'm mostly now using MLC's Krystal conversion varnish with 5% retarder.
My process of spraying the door would be to spray all 4 edges then spray a coat with 50% overlaps "with the grain" of the door center panel, then an additional coat with 50% overlap perpendicular to the previous coat. (No wait time in between these coats, mind you. So maybe this is my issue?) The first coat that goes "with the grain" is not terribly heavy either. I try to put it down very lightly. Trying to achieve a "misted" look. Then with the follow up perpendicular coat that will get me to my 3-4 wet mil thickness.
When I'm spraying a door that has square edges, and no roundovers, I don't run into this issue because I'm not doubling down on coats by spraying the edge and face.
Today I started a new job, with doors that have this 1/4" roundover on the edge, with a new theory. Using Krystal sealer to start sealing the doors. I sprayed the face of the door only. No edges sprayed. I'm thinking of only spraying the edges when I'm spraying the back of the door only because then there are no exposed roundovers?
I don't know. I used to fly through this stuff and never have any technical problems when I was using just a gravity fed cup hvlp gun.
the Small CAT pumps are 15:1 ratio so at 40 psi that is 600 psi fluid pressure. You should be spraying around 275 psi... my guess is your first pass is more like 5-6 wet mils then you are adding another wet pass of 4-6 wet mils over that. Have you sacrificed a real example and stuck a wet mil gauge immediately onto the surface after each pass to confirm or is it just a guess? The 411 tip should be just fine for the finish your using...... I bet backing off fluid pressure and speeding up your passes is going to dial it in better.... also try to give it a couple minutes to flash before your second wet pass...
I'm no expert, but 40/20 seems awfully high! I shoot mostly Duravar thinned 10-15% at 30/13 and it flows like a dream. With pigments like Resistant I have trouble and have to go up to 36/16 or so. The higher you go on the fluid pressure your really applying a lot of material. I would do a test piece and try starting at 30/13 or so and see what happens, that 40/20 setting may be the problem. You might get better results. Or alternatively watch the CAT videos of how to set your gun, gradually easing the pressure while watching the pattern. I haven't done it in years as I got used to a certain setting, but it may help you out.
As for doors.... I spray the edges 2 passes each, so I'll spray 1 edge and one end one direction, and then back again. Rotate the door and do the next 2. Then across the face of the door in a box pattern and it's good!
for MLC's Krystal CV i use 30 on the fluid and 12 on the air with the trigger pulled.. Staright out the can.
Again thanks guys.
So, I tried the 30/13 psi settings on the CA Tech AAA pump for spraying ML Campbell's Krystal. I ended up needing to up the atomizing pressure to 20psi give or take to get rid of the tails. I'm currently retarding the kyrstal 10%. And I am still getting runs on roundovers.
I took a sacrificial door and did a wet mil test while spraying the other doors of the job and I'm spraying a top coat that is ending up barely a 4 wet mil thick. Getting runs on those edges with the roundovers.
I tried just spraying the edges of the door when I'm spraying the backs and then just spraying the face of the door only when I switch to the face so that way I'm not double coating that roundover radius. However the edge loses its sheen smooth feel because it is essentially getting hit with overspray from just hitting the face without the edge.
Somehow I'm either making my product too thin with my 10% catalyst and 10% retarder and/or my technique sucks. I am box coating.